Dynamics of Tethered Polymers

Christopher Lueth Undergraduate Institution: University of Minnesota

Polymer physics has a rich tradition spanning nearly two centuries. Recently however, the development of DNA single molecule fluorescence microscopy coupled with ever increasing computational power has opened the door to molecular level understanding of polymer physics,
resolving old disputes and uncovering new interesting phenomena. In this work, we use a combination of theoretical and numerical predictions and single molecule fluorescence microscopy to study the behavior of polymers tethered to surfaces.

Experiments of tethered lambda-phage DNA in shear flow are presented for the first time in the flow-gradient plane. Successful tethering surface chemistry was achieved with the aide of contact angle and ellipsometry measurements. Brownian dynamics simulations of multiple polymer models - dynamic and equilibrium Kratky-Porod chains as well as bead-spring chains - were constructed and compared with analytical and experimental results. Both simulations and experiments display cyclic dynamics - where the polymer continuously diffuses away from the wall, subsequently stretches out, is then pulled back towards the wall, and finally recoils - and can be quantified through extension, distance from the wall, orientation angle correlations and power spectral densities. Cyclic dynamics occur for intermediate flow strengths, where interplay between diffusion perpendicular to the wall and flow parallel to the wall is greatest.